Children's anxiety symptoms and salivary immunoglobulin A: A mutual regulatory system?

Anxiety can impact the immune system resulting in negative health outcomes. Salivary immunoglobulin A (sIgA) is a first line of defense against foreign antigens, with lowered levels indicative of weakened mucosal immunity. Little is known about how anxiety symptoms affect the diurnal rhythm of sIgA secretion, or the longitudinal transactional sequence between the two in children and adolescents. The goals of the two studies were to: (i) explore the concurrent associations between self-reported anxiety symptoms and diurnal variations of sIgA across the day using repeated daily samples of sIgA; and (ii) examine transactional relations between children's anxiety and aggregated total amount of sIgA levels across successive periods from middle childhood (Wave 1; ages 9-12) to early adolescence (Wave 2; ages 12-15), and from early to mid- adolescence (Wave 3; ages 15-18). Concurrent results showed a steeper (positive) rise in diurnal slope of sIgA from awakening to 5 hr post-awakening in children with higher anxiety. Longitudinally, higher levels of total anxiety, and specifically, worries at Wave 1 significantly predicted lower cumulative daily levels of sIgA 3 years later at Wave 2. Lowered sIgA levels at Wave 2 in turn predicted higher anxiety at Wave 3, illustrating a "vicious cycle" feedback loop. These findings broaden our understanding of the developmental links between anxiety symptoms, the immune system, and health.